Pressure switch



y 5, L. BEEMAN ETAL 2,281,544

PRESSURE SWITCH Filed May 8, 1939 2 Sheets-Sheet l INVENTOR. fl wl vm/ ATTORNEY.

y 1942- 1.. BEEMAN E'l AL 2,281,544

PRESSURE SWITCH Filed May 8,-1939 2Sheets-Sheet2 w 1 2a a7 34/ 3'2 34/ 37 v H I 59 a? 33 1"""l 44 F j W iii molwa.

ATTORNEY.

Patented May 5, 1942 PRESSURE SWITCH Lyle Beeman, Milwaukee and Edwin W. I,

- Hanke, Whitefish Bay, was,

assignors to Allen- Bradley Company, Milwaukee, Win, a corporation of Wisconsin Application May 8, 1939, Serial No. 272,388

11 Claims. (Cl. 200-48) This invention relates to pressure responsive switches and resides in a novel, simplified arrangement of parts in which a principal resilient element opposes the force to be controlled, the same being supplemented by a preloaded resilient member, the supplementing force of which is active through a part only of the travel of the principal resilient member and in which an over center, snap action mechanism is driven by displacement of the principal resilient member in suchmanner that the forward over center position thereof occurs while the supplemental resilient member is exerting its supplemental action and the return over center position occurs while the principal resilient member is acting without supplement.

' showing the relationship of the parts One object of this invention is to produce ii.v

pressure switch which is compact to a degree greater than can be obtained in the case of pressure switches using the arrangement of parts heretofore employed and in which theprincipal resilient member resisting the actuating force is preferably in the form of a plate spring.

Another object of this invention is to provide a pressure switch in which a U-shaped frame memher my be employed, to the exterior of which a diaphragm and diaphragm chamber may be attached and within which the parts acted upon by the diaphragm may be accommodated and supported.

Another object of this invention is to provide apressure switch in which the principal resilient member is held in position without complicated supporting means and in a manner'permitting movement thereof with a minimum of friction.

Another object of this invention is to provide a pressure switch having an over centersnap action on both its forward and return strokes, the response pressures of each of said over center positions being independently adiustable without varying the intensity of the snap action eflect.

Her'etofore in the art a wide variety of forms of pressure switches have been employed in which the switch members themselves are moved with a snap action and in which the prmsures at which the switch functions are'subiectto resulation. In order to obtain the pressure response desired and the regulation desired these switches have employed a complex arrangement of Parts which is difilcult and expensive to construct and which is ill adapted to compact formation. Through this invention, however, a switch is provided which is free of the above objections and which is of the novel advent-see herein detailed. a

to a specific embodiment thereof descrmed in conjunction with the accomp y ns drawings which form a part hereof, the same being-act forth by way of illustration only and not of limitation. In the drawings: I Fig. 1 shows a side sectional view of a form of the pressure switch of this invention;

Fig. 2 is a plan view, partly in section and with parts broken away, of the switch shown in Fig.1: Fig. 3 is an end elevation, with parts broken away, of the switch shown in l 'lg. l: Fig.4isanenlargeddetailofsomeofthe movable parts of the switch shown in 1'18. 1.

in different positions; and

Fig. 5 is a fragmentary detail showing the method of anchorage of .the primary regulating screw.

The switch shown in the drawings derives its structural support from a U-shaped frame member I, which is shaped to form three sidesof a rous y rectangular box. The side corresponding to the bottom of the'U is engaged on its exterior face by a diaphragm 2 composed of any suitable flexible material, such as rubberized fabric, the same beingseeurely held in place by screws 0. which pass through a diaphrasm chamber I into threaded holes provided therefor in the frame I. Suitable means I for connection of the diaphragm chamber 4 with a pressure conduit is securely united with the diaphragm chamber... as shown.

The face of the frame I engaged by the diaphragmlispressedupwardlyabovethediaphragm and perforated to to a pressure-communicating member composed of a pressure-foot I and a thruster I. The thruster 'I'includes. two spaced apart. upwardly projecting prongs, as indicated by dotted lines in Fig. 2.

Mounted above the thruster I is a primary resilient opposing member s in the form of a plate spring. The spring I includes a raised portion 0. which acts as a thruster seat, which seat is engagedby the. mom of the thruster .1. The resilient portion of plate spring 8 extends to the leftof thethrusterseat ,asshowninligai and 2, and is held in position to perform its properfunction by a pair of ears it, which ex tend laterally therefrom at the mid point of its return curve. The cars II in turn engage moimting notches I I, formed by pressing inwardly-the material of theupstanding portions of frame I, asshown. Thetaperedre-entrantporflon "of the plate spring I is notched,as-shownat-ll,

for engagement with an adjusting nut I4, which is carried upon anchoring bolt I5 and in this manner the resilient opposition to movement of diaphragm 2 is subject to regulation by adjustment of nut I4.

Extending to the right of the thruster seat 9 is an integrally formed portion of the plate sprin 8, which, fbecause of pressed-up stifiening ribs I8,

is cut away in its central part to accommodate. the elements of a snap-action mechanism of the over center type. This "mechanism is pivoted upon a bracket I I8 which projects upwardly through the opening in plate spring 8 and which is securely riveted in place upon frame member I. Bracket I8 bears near its upper end a horizontal groove serving as a seat for a knife edge. Mounted to rock in the groove in bracket I8 is a toggle link I8, which is generally T-shaped in form and which is brought to a sharpened edge at the base of the T for engagement with the bracket I8. A

pair of toggle springs 20 join the links 'I9'with theplate spring 8 under tension to impart to the toggle link I9 over centersnap action properties. Springs 28 also serve the function of holding the ears III of the plate spring 8 against the notches II. A raisedportion 2I of the frame I serves as a lower stop for the toggle link I9, while an actuator bar 22 of a switch 23 serves as an upper stop for the toggle link I8. t

For the purpose of furnishing plate spring 8 with a specific amount of resilient reenforcement during a predetermined portion of its stroke, ad

justable auxiliary spring 24 is provided. The auxiliary spring 24 is held in place and guided by guide washers 25, which'in turn are carried upon threaded post 28. Post 2815 rigidly secured to the bottomof frame member I, as by a rivet head 21, this rivet serving the dual purpose, if desired, of securing themounting post 28 in-place and holding the bracket I8, as shown. Post 28, further, is provided with an enlarged portion or shoulder, 28, against which lower guide washer 25 comes, to rest, thus preventing any further downward displacement of the lowerend of auxiliary spring 24. The upper guide washer 25 i adjustably held in place by means of the auxiliary adju sting nut 28 provided for that purpose.

The mode of operation of the parts above described is best explained by reference to enlarged detailed view, Fig; 4, wherein the parts are shown by full lines in the standing or o position. In this view, for the sake of clarity, toggle springs 28 are omitted and the line of action thereofindicated by 'dot-anddash lines. In the standing or "oifi position, due to the line of action of toggle springs 20, toggle linkv I8 is brought to and held by stop 2| in the position of equilibrium shown by the full lines. As the tpressure exerted upon thruster 1 increases, plate spring 8 deflects accordingly and as such increase continues the lever end of plate spring 8 comes into engagement with guide-washer 25. Thereafter the thruster 1 acts against the combined resistance of the primary opposition of plate spring 8 and the auxiliary opposition of spring 24. Continued movement thereafter under the influence of the thruster, I brings the parts to the oint where the line of action of toggle springs is coincident with the major axis of the toggle I9. The line indicating this position is designated by the numeral 30. This position is herein referred to for convenience asthe "forward over center position," and is the position where, upon continued forward movement, the toggle linkage becomes unstable and passes with a snap action to the position shown by dotted lines. In so doing, the

toggle link I9 first gathers momentum and then strikes the switch-actuating bar 22, rapidly forcing the switch 28 to open position. Upon reduction of the effort applied through thruster I, a

return motion of the parts takes place in the following sequence: First, deflection in springs 8 and 24 diminishes to a point where spring 24 comes to rest'against shoulder 28 and, thereafter, continued movement of the parts brings them to a return over center position indicated by line 8|. It is here noted that during the return passage through the return over center position the thruster I is acting against the tension of plate spring 8 only, without the assistance of auxiliary spring'24. Continued motion in a return direction thereafter causes the toggle linkage to snap from the position indicated by dotted lines to the position shown in Fig. 4 by full lines.

By reason of the sequence of movements above described, the pressure switch of this invention may be adjusted with great-ease. For example,

if the switch is to be employed toregulate a pump supplying fluid to a pressure reservoir and ,it is desired that .the pump go 'intogoperation when pressures 'in the reservoir drop below a designated low-pressure limit, the adjusting nut I4 may be turned until the desired closing characteristics of the switch are-obtained. Then, if it is desired that the pump continue in operation until a designated high pressure limit isreached, the adjusting nut 29 is turned until the desired opening characteristics of the switch are obtained. If the adjustments are made in this sequence, the same may be made entirely independently of one another, since the return or closing characteristics of the switch are determined solely by the characteristics of the primary opposing resilient member 8 and theadjustment of nut I4. It is thus apparent that the normal differential between opening andclosing pressures, which is due to the characteristics 'of plate spring 8 and the geometry of the parts,

may be augmented to any degree desired by means of the auxiliary spring 24 and as far asthis differential is augmented the same is subject to independent adjustment through adjusting nut 29.

While the characteristics of spring 24 are relatively unimportant inobtaining the result above described, we prefer to employ for the purpose,

as shown, a pre-stressed resilient member, the

resilient reaction of which increases but slightly over the range of displacement employed. With by springing the sides of frame I while forcing the mounting 32 into position. The switch-actuating bar 22 above referred to is slidingly received and guided in slots formed in the lower side of insulating mounting I2 and carries a pair of loosely held contact bars-34 upon upwardlyprojecting lugs 35 provided therefor. To insure proper contact pressure, backing springs 39 are provided. The contact bars 34 are arranged to come into contact with lower contacts carried upon terminal members 36, which are received in lateral recesses in the insulating member 32 and held in place by terminal screws 31.

In order to prevent undue friction in the movement of plate spring 8, adjusting screw II is preferably mounted so that it is free to rock and this may be accomplished, as shown in Fig. 5, by receiving the dove-tailed foot 38 of screw IS in a deeply countersunk aperture in the frame member I, as shown.

To complete the enclosure of the switch, any suitable cover, not shown, may be provided, such as a strap, or belt, passing around the three open sides of the frame member I. Suitable conduit-admitting apertures, such as 40, may be provided, and it will be noted that by reason of the substantially parallel disposition of plate spring 8 with respect to diaphragm 2 that ample space for access to the switch 23, for wiring purposes, is easily obtained.

While this invention has been above described by reference to a specific instance of an embodiment thereof, it is intended that the protection of Letters Patent to be granted hereon be not unnecessarily limited thereby, but that such protection extend to the substance of the advance contained in this disclosure and defined in the claims hereto appended.

That which we claim as our invention and wish to secure by Letters Patent is:

1. In a pressure-actuated switch, the combination comprising a U-shaped frame member, a diaphragm and diaphragm chamber secured to the exterior of the bottom of said frame member, a presser-foot engaging said diaphragm provided with a thruster extending into the interior of said frame member, a plate spring having a return bend pivotally carried near said bend upon pivot supports associated with said frame member, said spring being in engagement with said thruster to be deflected thereby, means for adjustably engaging one end of said spring for adjustably tensioning the same, over center snapaction means engaging the opposite end of said spring, and a circuit-interrupting means mounted within said frame member in position to be actuated by said over center snap-action means.

2. In a pressure responsive switch, the combination comprising a mounting frame, a diaphragm and diaphragm chamber secured to one side thereof, a deflectable plate spring mounted on the opposite side thereof and positioned substantially parallel to said diaphragm, a presserfoot engaging said diaphragm and provided with a thruster which extends therefrom through said frame into cooperative engagement with said spring, toggle means including a toggle link and toggle tensioning means associated with said plate spring to be actuated thereby and having a forward and a return over center position, and an auxiliary spring positioned to engage and reenforce said plate spring while passing through said forward over center position only, and circuit-interrupting means actuatable by said toggle means.

3. In a pressure switch of the class described, the combination comprising a U-shaped frame member having a bottom portion and upstanding side portions, apertures in said side portions, circuit-interrupting means between said side portiOns and secured in place by engagement with said apertures, pressed-in notches oppositely positioned upon the interior of each of said frame side portions, a plate spring having sidewardly projecting ears engaging said notches, means for adjustably locating said plate spring, means for communicating actuating force to said plate spring, and means associated with said plate spring for actuating said circuit-interrupter.

4. In a pressure responsive switch, the combination comprising a plate spring having a bent portion and two ends extending therefrom, means for adjustably locating one end thereof, means for pivotally restraining said spring near the bent portion thereof, means for communicating operating pressures to the opposite end of said spring, a toggle link pivotally carried in position to be actuated by said spring and enga n the same through resilient means tensioned so as to hold the bent portion of said spring in engagement with said pivotally-restraining means, auxiliary adjusting means engaging said spring, and a circuit-interrupter actuatable by said toggle link.

5. In an apparatus differentially responsive to fluctuating actuating force, the combination comprising a primary resilient means, means for communicating fluctuating actuating force to said primary resilient means for deflecting the same from a position of lower stress to a position of higher stress, a toggle member pivoted to turn about a stationary pivot associated with said primary resilient means having a position of equilibrium corresponding to said position of higher stress and a position of equilibrium corresponding to said position of lower stress and having spaced forward and return unstable over center positions corresponding to spaced intermediate positions of said primary resilient means, and auxiliary resilient means positioned to reenforce said primary resilient means during forward movement thereof through said forward over center position and to release said reenforcement prior to return movement of said primary resilient means through said return over center position.

6. In anapparatus responsive to fluctuating actuating force, the combination comprising a plate spring having a bent portion and two ends extending therefrom, means for adjustably locating one end thereof, means for pivotally restraining said spring near the bent portion thereof, means for communicating said fluctuating actuating force to the opposite end of said spring for deflecting the same, a toggle link pivotally carried on a stationary pivot in position to be actuated by said spring upon deflection thereof and engaging said spring through resilient means stressed so as to hold the bent portion of said spring in engagement with said pivotally-restraining means, and auxiliary adjusting means for engaging said spring during a portion of the travel thereof,

7. In a pressure-responsive switch, the combination comprising a frame member having a base portion, a diaphragm chamber secured to the exterior surface of said base portion, a diaphragm clamped between said chamber and said base portion, a presser-foot engaging said diaphragm provided with a thruster extending through said base portion to the interior side thereof, a plate spring disposed close to and in nearly parallel relation with the interior sur- 7 face of .said' base portion in position to be deflected away from said base portion by said thruster, means adjustably engaging said spring for adjustably tensioning the same, over-center snap action means cooperatively engaging a deflectable portion of said spring, and a circuit interrupting means associated with said base in position to be actuated by said over-center snap action means 1 8, In a pressure-responsive switch, the combination comprising a frame member having a base portion, a diaphragm chamber secured to the exterior surface of said base portion, a diaphragm clamped between said chamber and said base portion, a presser-foot engaging said diaphragm provided with a thruster extending through said base portion to the interior side thereof, a plate spring disposed close to and in nearly parallel relation with the interior surface of said base portion in position to be deflected away from said base portion by said thruster, means adjustably engaging said spring for adjustably tensioning the same, an aperture in said plate spring, toggle means including a toggle linkand toggle tensioning means mounted within said aperture to be actuated by said plate spring, and circuitinterrupting means actuatable by, said toggle 9. In a pressure switch, a sheet metal housing engagement with said diaphragm, a thruster extending from said-presser-foot through said base portion intothe interior of said housing, a platespring disposed above said rectangular base portion inapproximately parallel relation thereto, means associated with said base for causing said spring to oppose'the action of said thruster, contactor mounting 'means disposed in bridging relation between'and secured to said parallel side por-' tions of said housing, fixed and movable contacts mounted thereon, over-center snap action means associated with said springadapted to be actuated thereby when said spring is deflected by said thruster, and means for causing said overoenter means to act upon said movable contacts.

10. In a pressure-responsive switch, the combination comprising a frame member having a base portion having upstanding side portions open at the top, a diaphragm'chamber secured to the bottomexterior surface of said base, a diaphragm clamped between said chamber and said base, a presser-foot engaging said diaphragm and provided with a thruster extending upwardly means, and terminals on said circuit-interrupting means accessible from a position above said a spring and over-center snap action means.

11. In a pressure-responsive switch, the combination comprising a frame member having a base portion having upstanding side portions open at the top, a diaphragm chamber secured to the bottom exterior surface of said base, a diaphragm clamped between said chamber and said base,-a presser-foot engaging said diaphragm and provided with a thruster extending upwardly through said aperture to be actuated by said plate-spring,

circuit-interrupting means mounted upon said base and spring and above said toggle means in position to be actuated thereby, and terminals on said circuit-interrupting meansaccessible from a position above said base, spring, and toggle means.

LYLE IBEEMAN. EDWIN w. F, mums, 

